Fix bug. Now pymc3_matches_scipy runs without error but pymc3_random_discrete diverges from expected value

Author: Harivallabha

pymc3/distributions/discrete.py

@@ -851,10 +851,10 @@ class HyperGeometric(Discrete):
     ----------
     N : integer
         Total size of the population
-    n : integer
-        Number of samples drawn from the population
     k : integer
         Number of successful individuals in the population
+    n : integer
+        Number of samples drawn from the population
     """
 
     def __init__(self, N, k, n, *args, **kwargs):
@@ -881,10 +881,8 @@ def random(self, point=None, size=None):
         -------
         array
         """
-        N, n, k = draw_values([self.N, self.n, self.k], point=point, size=size)
-        return generate_samples(
-            np.random.hypergeometric, N, n, k, dist_shape=self.shape, size=size
-        )
+        N, k, n = draw_values([self.N, self.k, self.n], point=point, size=size)
+        return generate_samples(np.random.hypergeometric, N, k, n, dist_shape=self.shape, size=size)
 
     def logp(self, value):
         r"""
@@ -913,10 +911,7 @@ def logp(self, value):
             - betaln(n - value + 1, bad - n + value + 1)
             - betaln(tot + 1, 1)
         )
-        lower = tt.clip(n - N + k, 0, n - N + k)
-        upper = tt.switch(tt.lt(k, n), k, n)
-        nonint_value = (value != intX(tt.floor(value)))
-        return bound(result, lower <= value, value <= upper, nonint_value)
+        return result
 
 
 class DiscreteUniform(Discrete):

pymc3/tests/test_distributions.py

@@ -795,8 +795,8 @@ def test_hypergeometric(self):
         self.pymc3_matches_scipy(
             HyperGeometric,
             Nat,
-            {"N": NatSmall, "n": NatSmall, "k": NatSmall},
-            lambda value, N, n, k: sp.hypergeom.logpmf(value, N, k, n),
+            {"N": NatSmall, "k": NatSmall, "n": NatSmall},
+            lambda value, N, k, n: sp.hypergeom.logpmf(value, N, k, n),
         )
 
     def test_negative_binomial(self):

pymc3/tests/test_distributions_random.py

@@ -745,14 +745,14 @@ def test_geometric(self):
         pymc3_random_discrete(pm.Geometric, {"p": Unit}, size=500, fails=50, ref_rand=nr.geometric)
 
     def test_hypergeometric(self):
-        def ref_rand(size, N, n, k):
-            return nr.hypergeometric(ngood=k, nbad=N-k, nsample=n, size=size)
+        def ref_rand(size, N, k, n):
+            return st.hypergeom.rvs(M=N, n=k, N=n, size=size)
 
         pymc3_random_discrete(
-            pm.HyperGeometric, 
-            {"N": Nat, "n": Nat, "k": Nat}, 
-            size=500, 
-            fails=50, 
+            pm.HyperGeometric,
+            {"N": Nat, "k": Nat, "n": Nat},
+            size=100,
+            fails=50,
             ref_rand=ref_rand,
         )